Prior art intraurethral magnetic valves have relied on a wide variety of different magnetic valve configurations that attempt to control the fluid flow from the bladder. Examples of same can be defined and divided into three basic designs. The first design group is characterized by ferromagnetic spheres or slugs which seal an aperture by attraction to one or more fixedly located permanent magnets within a valve housing or are resiliently held in closed position by a spring, and are drawn or tilted away from the aperture by a strong permanent magnet or electromagnetic field induced by a hand-held magnet located outside the valve housing, see for example, U.S. Pat. Nos. 3,731,670, 5,004,454 and 5,140,999.
The second design group is characterized by permanent magnets bonded to nonmagnetic valve checks which are drawn to seal an aperture by attraction to a ferromagnetic element comprising all or part of an apertured valve seat or are resiliently held in closed position against the valve seat by a spring. These checks are drawn in a straight linear motion away from the apertured valve seat by a hand-held magnet outside the valve housing, see for example, U.S. Pat. No. 3,812,841.
The third design is characterized by a valve check containing a permanent cylindrical magnet and sealing in an arbitrary position against a planar valve seat of ferromagnetic material. This check is tilted off the valve seat by magnetic torque induced between the poles of an external hand-held switching magnet and the internal check magnet, see for example, U.S. Pat. No. 5,366,506, issued to the present inventor.
In U.S. Pat. No. 3,731,670, a corporeal fluid control using binary magnetic duct valve is disclosed wherein a mounting tube has two spaced magnets with a steel ball valve element therebetween. The ball valve element is selectively attracted to each of the magnets defining an open or closed state depending on which magnet the ball is engaged. The ball is reciprocated within the structure by an external magnetic force.
U.S. Pat. No. 5,004,454, is directed to an intraurethral magnetic valve. A valve element of a ferromagnetic material is held in sealing relation against a valve seat by a spring associated therewith. The valve is opened by imposing a magnetic force on the valve element drawing same away from the seat and stretching the spring.
U.S. Pat. No. 5,140,999, is directed to an implantable valve structure in which the valve element extends well within the bladder for increased lateral operational movement. The valve element has a compression spring engaging same in a closed or checked position. Upon inducement of an outside magnetic force the magnetizable member on the free end of the valve element within the bladder is displaced to the side moving the respective valve element off its valve seat opening the valve. No accommodation is made for bladder neck movements or changes in bladder inflation which may cause unwanted movements of the free end of the valve element.
The devices defined by the first group of prior art valves suffer from an intrinsic difficulty in balancing the magnetic force needed for adequate sealing with the need for reasonable operational range of the activation magnet.
Since magnetic forces are highly nonlinear, decreasing very rapidly with distance from the magnetic poles; when a ferromagnetic ball or slug is held against an apertured valve seat by a permanent magnet element, the respective switching magnet must be either very large or very close to induced the required force. The slug checks that are drawn to the side of the housing encounter high sidewall friction forces which are induced increasingly as the angle between the housing center line and the line of approach of the switching magnet increases.
In U.S. Pat. No. 3,812,841, a urethra magnetic valve structure can be seen in which a valve element is positioned on a movable magnetic core cylinder. The valve element is held in closed position by an attached spring. Inducing a high electromagnetic force from outside the body will move the magnetic core cylinder and valve element attached thereto opening the valve.
In U.S. Pat. No. 3,812,841, the valve check movement is constrained by the housing to a straight line which necessitates that unless the switching magnet approaches with its axis directly aligned on the center line the force will draw the check against the sidewall imparting torque induced friction decreasing the effectiveness and movement of the check with the valve housing.
The valve assembly in U.S. Pat. No. 5,366,506 overcomes the drawbacks of small working distance and sidewall friction associated with devices of the first and second design groups, but can exhibit high fluid drag and low fluid flow rates in a valve-open position due to the limited clearance between the valve check, containing a cylindrical magnet, and the sidewalls of the valve assembly's housing. Another embodiment of the valve assembly in U.S. Pat. No. 5,366,506 provides for a magnetic valve check hingedly attached to the housing of the valve assembly which can provide higher fluid flow rates in a valve-open position.
The present invention is directed to a magnetic valve providing an enhanced fluid flow rate therethrough in a construction which reduces the ratio between fluid drag and overall valve diameter. The magnetic valve includes a spherical magnet valve element which sealingly engages a nonferromagnetic valve seat by attraction to a ferromagnetic ring. The valve seat and the ferromagnetic ring comprise a valve seat assembly which is sealingly attached to an inner bore of a cylindrical nonmagnetic valve housing. Under an initial weak action of an approaching hand-held switching magnet, the valve element rotates in the valve seat, causing renal calculus and mucous deposits to be wiped off the valve element by the valve seat. Under stronger action of magnetic attraction induced by closer proximity of the switching magnet to the magnetic valve element, the valve element moves from the valve seat and thereby opens a valve lumen to fluid flow therethrough.
The magnetic valve of the present invention may further include a mechanism for relieving excessive fluid pressure, in which the valve seat assembly is slidable in an axial direction in the housing instead of being attached to the housing, and resiliently held by a compression spring in sealing engagement with an annular flange which is sealingly attached to the inner bore of the valve housing. The spring is constructed to define a condition of high fluid pressure relief. Under a condition of high fluid pressure, the valve element and the valve seat assemblies are displaced together in an axial direction within the housing so as to further compress the spring and thereby to permit slow release of fluid through a passageway around the valve seat assembly so as to reduce the high pressure condition. The provision of high pressure relief is particularly important in addressing a common and medically dangerous problem of high intravesical pressure caused in spinal cord injury patients by uncontrolled detrusor muscle contractions. Under normal conditions, the valve assembly is in sealing engagement with the annular flange, enabling the valve element and valve assembly to function responsive to the switching magnet, as described above.